The present invention relates to a switch-device sheet in which a light guiding member is provided on a soft and elastic sheet body having operation parts.
In a conventional vehicular switch device, for example, a light guiding member is installed on a soft and elastic sheet body which is made of, for example, silicone rubber, and has an operation part (contact operation part) for operating switch contacts.
The light guiding member is generally formed with a transparent and hard synthetic resin block; and is embedded in the sheet body. A light emitting body is located just under or near the light guiding member. The light guiding member receives light emitted from the light emitting body at one end, and emits the light at the other end, and operation knobs of the switch device, the display section, or the like are illuminated.
In the conventional switch device, the sheet body is soft and elastic, but the light guiding member is formed with the hard synthetic resin block. Therefore, the resultant switch-device sheet is not flexible as a whole. Accordingly, a place to attach the switch-device sheet is limited to a flat plane portion, while avoiding a curved portion.
The light guiding member of the hard synthetic resin block is not flexible in design also of its size and configuration. Accordingly, a light emitting position on the other end of the light guiding member in the sheet body is limited in its selection by the size and configuration of the light guiding member. Additionally, the distance between the light emitting body and the operation knob is also limited in its selection by the size and configuration of the light guiding member.
Further, the conventional switch device is known, which includes a light source, such as a light emitting diode or a bulb, to illuminate a display section presenting the contents on operations of the light guiding device, and a light guiding member for guiding light emitted from the light source to the display section.
The light guiding member is made of a material of a high optical transmittance, such as acrylic resin.
Incidentally, there is a light transmission plate in which a light diffusion layer is provided on the reverse side of a transparent light guiding member (see JP-A-05-11117, for example), although it has no direct relation to the problem to be solved by the present invention.
In a device having the conventional light guiding member, light passing through the light guiding member leaks from a surface of the light guiding member parallel to the light guiding direction since the light is scattered inside the light guiding member. For this reason, the optical directivity of the light guiding member is not good, and the illumination efficiency is not satisfactory in illuminating the display section with light emitted from the light source.
In further another conventional vehicular switch device, a light guiding member is installed on a soft and elastic sheet body which is made of, for example, silicone rubber, and has an operation part (contact operation part) for operating switch contacts. In this switch device, the light guiding member may be handled together with the sheet body. Accordingly, the switch device is excellent in its assembling.
The light guiding member of the switch device is formed with a transparent and hard synthetic resin block, such as acrylic resin. And it is embedded in the sheet body. A light emitting body is located just under or near one end of the light guiding member. The light guiding member receives light emitted from the light emitting body at one end and guides the light, and emits the light at the other end. The guided light illuminates operation knobs of the switch device, the display section, or the like.
In the conventional switch device in which the sheet body contains the light guiding member, the sheet body is soft and elastic, but the light guiding member is formed with the hard synthetic resin block. Therefore, the whole of the resultant switch-device sheet is not flexible. Accordingly, a place to attach the switch-device sheet is limited to a flat plane portion, while avoiding a curved portion.